docs: def deserialize_tag(stream, header, verifier=None):
      """Deserialize the Tag value from a non-framed stream.
  
      :param stream: Source data stream
      :type stream: io.BytesIO
      :param header: Deserialized header
      :type header: aws_encryption_sdk.structures.MessageHeader
      :param verifier: Signature verifier object (optional)
      :type verifier: aws_encryption_sdk.internal.crypto.Verifier
      :returns: Tag value for body
      :rtype: bytes
      """
      (data_tag,) = unpack_values(
          format_string=">{auth_len}s".format(auth_len=header.algorithm.auth_len), stream=stream, verifier=verifier
      )
      return data_tag